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LPD(8) NetBSD System Manager's Manual LPD(8)
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lpd -- line printer spooler daemon
lpd [-dlsrW] [-b bind-address] [-n maxchild] [-w maxwait] [port]
lpd is the line printer daemon (spool area handler) and is normally
invoked at boot time from the rc(8) file. It makes a single pass through
the printcap(5) file to find out about the existing printers and prints
any files left after a crash. It then uses the system calls listen(2)
and accept(2) to receive requests to print files in the queue, transfer
files to the spooling area, display the queue, or remove jobs from the
queue. In each case, it forks a child to handle the request so the par-
ent can continue to listen for more requests.
-b Normally, if the -s option is not specified, lpd will listen on
all network interfaces for incoming TCP connections. The -b
option, followed by a bind-address specifies that lpd should lis-
ten on that address instead of INADDR_ANY. Multiple -b options
are permitted, allowing a list of addresses to be specified. Use
of this option silently overrides the -s option if it is also
present on the command line. bind-address can be a numeric host
name in IPv4 or IPv6 notation, or a symbolic host name which will
be looked up in the normal way.
-d The -d option turns on the SO_DEBUG socket(2) option. See
setsockopt(2) for more details.
-l The -l flag causes lpd to log valid requests received from the
network. This can be useful for debugging purposes.
-n The -n flag sets maxchild as the maximum number of child pro-
cesses that lpd will spawn. The default is 32.
-r The -r flag allows the ``of'' and ``if'' filters to be used if
specified for a remote printer. Traditionally, lpd would not use
filters for remote printers.
-s The -s flag selects ``secure'' mode, in which lpd does not listen
on a TCP socket but only takes commands from a UNIX domain
socket. This is valuable when the machine on which lpd runs is
subject to attack over the network and it is desired that the
machine be protected from attempts to remotely fill spools and
-w The -w flag sets maxwait as the wait time (in seconds) for dead
remote server detection. If no response is returned from a con-
nected server within this period, the connection is closed and a
message logged. The default is 120 seconds.
-W The -W option will instruct lpd not to verify a remote tcp con-
nection comes from a reserved port (<1024).
If the [port] parameter is passed, lpd listens on this port instead of
the usual ``printer/tcp'' port from /etc/services.
Access control is provided by three means. First, /etc/hosts.allow and
/etc/hosts.deny are consulted as described in hosts_access(5) with daemon
name lpd. Second, all requests must come from one of the machines listed
in the file /etc/hosts.equiv or /etc/hosts.lpd unless there is a line
consisting of `+', in which case any host will be accepted that passes
the hosts_access(5) test and has reverse resolving set up. Lastly, if
the rs capability is specified in the printcap(5) entry for the printer
being accessed, lpr requests will only be honored for those users with
accounts on the machine with the printer. Requests must pass all three
The file minfree in each spool directory contains the number of disk
blocks to leave free so that the line printer queue won't completely fill
the disk. The minfree file can be edited with your favorite text editor.
The daemon begins processing files after it has successfully set the lock
for exclusive access (described a bit later), and scans the spool direc-
tory for files beginning with cf. Lines in each cf file specify files to
be printed or non-printing actions to be performed. Each such line
begins with a key character to specify what to do with the remainder of
J Job Name. String to be used for the job name on the burst page.
C Classification. String to be used for the classification line on
the burst page.
L Literal. The line contains identification info from the password
file and causes the banner page to be printed.
T Title. String to be used as the title for pr(1).
H Host Name. Name of the machine where lpr(1) was invoked.
P Person. Login name of the person who invoked lpr(1). This is
used to verify ownership by lprm(1).
M Send mail to the specified user when the current print job com-
f Formatted File. Name of a file to print which is already format-
l Like ``f'' but passes control characters and does not make page
p Name of a file to print using pr(1) as a filter.
t Troff File. The file contains troff(1) output (cat phototypeset-
n Ditroff File. The file contains device independent troff output.
d DVI File. The file contains Tex l output DVI format from Stan-
g Graph File. The file contains data produced by plot.
c Cifplot File. The file contains data produced by cifplot.
v The file contains a raster image.
o The file contains PostScript data.
r The file contains text data with FORTRAN carriage control charac-
1 Troff Font R. Name of the font file to use instead of the
2 Troff Font I. Name of the font file to use instead of the
3 Troff Font B. Name of the font file to use instead of the
4 Troff Font S. Name of the font file to use instead of the
W Width. Changes the page width (in characters) used by pr(1) and
the text filters.
I Indent. The number of characters to indent the output by (in
U Unlink. Name of file to remove upon completion of printing.
N File name. The name of the file which is being printed, or a
blank for the standard input (when lpr(1) is invoked in a pipe-
If a file cannot be opened, a message will be logged via syslog(3) using
the LOG_LPR facility. lpd will try up to 20 times to reopen a file it
expects to be there, after which it will skip the file to be printed.
lpd uses flock(2) to provide exclusive access to the lock file and to
prevent multiple daemons from becoming active simultaneously. If the
daemon should be killed or die unexpectedly, the lock file need not be
removed. The lock file is kept in a readable ASCII form and contains two
lines. The first is the process id of the daemon and the second is the
control file name of the current job being printed. The second line is
updated to reflect the current status of lpd for the programs lpq(1) and
/etc/printcap printer description file
/var/spool/output/* spool directories
/var/spool/output/*/minfree minimum free space to leave
/dev/lp* line printer devices
/var/run/printer socket for local requests
/etc/hosts.allow explicit remote host access list.
/etc/hosts.deny explicit remote host denial of service list.
/etc/hosts.equiv lists machine names allowed printer access
/etc/hosts.lpd lists machine names allowed printer access,
but not under same administrative control.
lpq(1), lpr(1), lprm(1), setsockopt(2), syslog(3), hosts.equiv(5),
hosts_access(5), hosts_options(5), printcap(5), lpc(8), pac(8)
4.3 BSD Line Printer Spooler Manual.
An lpd daemon appeared in Version 6 AT&T UNIX.
NetBSD 6.0 January 20, 2006 NetBSD 6.0